HOW TO- design something for alerts when it reaches a certain point

Thread Starter

Electroman123

Joined May 26, 2022
5
Hello, I’m needing some help trying to creat something. I need something to be able to alert me when something reaches a certain sensor. For example, How a digital rain gauge is able to detect when rainfall hits the 1 inch mark. Im not too familiar with what goes into that stuff. Anyone who might be able to help, feel free to respond and I can fill you in on more information. Thanks.
 

dl324

Joined Mar 30, 2015
14,466
Welcome to AAC!

Does the digital rain gauge in question have such an alarm capability? If not, does it have any auxiliary outputs that you can use?

If you build your own, you just need something to detect water level in the collection vessel and trigger an alarm at the desired level. Positioning of the sensor matters.
 

Papabravo

Joined Feb 24, 2006
18,424
The basic idea is to convert physical measurements like "an inch of rain" into some electrical quantity like voltage or current that can be measured, recorded, stored, and processed. Secondary to this process we need two auxiliary processes. The first will convert continuous analog data into a series of discrete digital samples. The second process will convert a sequence of digital samples into a replica of the original analog waveform.
 

Thread Starter

Electroman123

Joined May 26, 2022
5
Thanks, Sorry I thought I posted it to a different category. I did explain it in my post, the rain gauge alerts and what I would need to get going on it on the electrical side of things.
 

Thread Starter

Electroman123

Joined May 26, 2022
5
Welcome to AAC!

Does the digital rain gauge in question have such an alarm capability? If not, does it have any auxiliary outputs that you can use?

If you build your own, you just need something to detect water level in the collection vessel and trigger an alarm at the desired level. Positioning of the sensor matters.
What is something that will detect and allow to transfer into that data? Obviously ill need sensors and so on.
 

Papabravo

Joined Feb 24, 2006
18,424
What is something that will detect and allow to transfer into that data? Obviously ill need sensors and so on.
A simple digital scale would work. You know the density of water, so you can measure the weight of a sample and compute the volume. From the geometry of the collection vessel, you can compute the height of the sample.
 

Thread Starter

Electroman123

Joined May 26, 2022
5
A simple digital scale would work. You know the density of water, so you can measure the weight of a sample and compute the volume. From the geometry of the collection vessel, you can compute the height of the sample.
Any recommendations of small scales what would work well with the size of average rain gauges?
 

dl324

Joined Mar 30, 2015
14,466
What is something that will detect and allow to transfer into that data? Obviously ill need sensors and so on.
Do you want this for a fixed level of water?

I've used this:
1653577054393.png
As I recall, it uses a quad CMOS NAND or hex inverter to detect contact closure and drive a speaker/transducer.
 

BobTPH

Joined Jun 5, 2013
4,907
Please tell us, in more detail, what you have and what you want to add to it. Your posts so far have not been clear.

Bob
 

Ya’akov

Joined Jan 27, 2019
5,663
Could you explain the problem the rain gauge is going to solve? Characterizing the problem is critical when trying to engineer a solution. If you make the rain gauge into the problem it can easily be solved without being a solution to the real problem you haven’t mentioned.

Also, most high accuracy digital rain gauges are based in the tilting bucket mechanism. A small container is mounted in such a way the it becomes overbalanced when full and tilts over emptying itself. When it tilts, it increments a count. You can imagine that it is like weighing the rain a tiny bit at a time and adding it up.
 

Reloadron

Joined Jan 15, 2015
6,585
You may want to start by giving this a read. Since you mention for example a 1.0" mark. Just one of many types of rain gauge. You can also just Google "how to measure rain precipitation" for more ideas. The next trick is once you get an inch or really any predetermined amount how to get a usable signal? You could weigh it or use a light beam across the sensor level. LASER transmitters and receivers are inexpensive. If your column of rain is in a plastic container drill a tiny hole at the base and one inch levels and insert a few pins measure the resistance. Make a tiny float switch. Depends on how you want to pursue it?

Ron
 

ErnieM

Joined Apr 24, 2011
8,294
...As I recall, it uses a quad CMOS NAND or hex inverter to detect contact closure and drive a speaker/transducer.
SERIOUSLY? I did a circuit like that over 40 years back so my Mom would get notice it was raining on her laundry out back. Also the battery check terminals would sense the dog was healthy by detecting his wet nose.

It ran for years off the first and only 9V battery put inside.
 

MisterBill2

Joined Jan 23, 2018
11,880
There are published plans for adjustable threshold analog limit detectors that have been around for years. Some of them use a comparator, others use a bunch of discrete components.. Search for "Watch Box" or "Alarm box". There have even been circuits discussed on threads at this site. Check through the lists of names. Butthose threads often contain a lot of guesses when the poster does not provide enough information at the start.
 

Tonyr1084

Joined Sep 24, 2015
6,891
I'm unfamiliar with how you use a rain gauge. On the surface it may seem intuitively simple. Collect an inch of rain - you have an inch of rain. But here's where my lack of familiarity shows itself - - - do you have to empty it after a rainfall, after you've seen or measured the amount of rain? Do you let it dry? Do you measure and empty on a schedule? My thinking is that if you capture an inch of rain - how do you reset the measurement for the next rain event? And - NO - I'm not looking for an answer to that question - I'm asking the TS if he's thought of that issue. Personally I don't need an answer; I just want to share what may be an issue to be contended with. I could google it if I wanted an answer - but I'm not because I'm not hijacking this thread. Moderators take note - I'm not hijacking!
 

Ya’akov

Joined Jan 27, 2019
5,663
I'm unfamiliar with how you use a rain gauge. On the surface it may seem intuitively simple. Collect an inch of rain - you have an inch of rain. But here's where my lack of familiarity shows itself - - - do you have to empty it after a rainfall, after you've seen or measured the amount of rain? Do you let it dry? Do you measure and empty on a schedule? My thinking is that if you capture an inch of rain - how do you reset the measurement for the next rain event?
From above:

Also, most high accuracy digital rain gauges are based in the tilting bucket mechanism. A small container is mounted in such a way the it becomes overbalanced when full and tilts over emptying itself. When it tilts, it increments a count. You can imagine that it is like weighing the rain a tiny bit at a time and adding it up.
As far as what period courts for measurement, it depends on application. It might be from inch to inch or rain, or a certain number of hours, or some other formula, The tilting buck type is effectively continuous measurement and the rest is what you want to do with the data.
 

Tonyr1084

Joined Sep 24, 2015
6,891
Members - keep in mind I'm asking the TS to consider the "Reset" process. I personally don't need an answer. I have a rain sensor on the roof. It's currently set that if 3/4 inch of rain fall will shut off the sprinklers. I have no desire to measure anything. The way my sensor works is there are some fiber pads that swell when wet. More rain more swelling. That swelling activates a microswitch to open the ground circuit in the sprinkler controller. No ground - no circuit for the sprinkler valves to operate. Water shuts off. After some time unbeknownst to me - the pads dry out and the sprinklers are able to run on schedule again.

Let me be clear before I get accused of hijacking a thread - I don't want or need an answer. I want the TS to consider that part of it. If you have a gauge that tips and empties itself at one inch, then detect the tip-over.
Also, most high accuracy digital rain gauges are based in the tilting bucket mechanism. A small container is mounted in such a way the it becomes overbalanced when full and tilts over emptying itself. When it tilts, it increments a count. You can imagine that it is like weighing the rain a tiny bit at a time and adding it up.
My thinking was on measuring the amount of rainfall. Whether it's an inch or a tenth of an inch, my thinking was how to measure that. Then suppose you get a tenth on Monday. Tuesday is warm, windy and dry. What was collected on Monday will likely have evaporated. Wednesday's rainfall may equal 95/100 of an inch and you still don't have your "Inch" of rainfall to tip the bucket.

Again - I'm not looking for an answer. I'm asking that these points be considered in the design of the TS measurement / alarm system.
 
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